[Arterial to end-tidal carbon dioxide difference during laparoscopy].

Arterial as well as end-tidal PCO2 (PaCO2, PetCO2), and arterial to end-tidal PCO2 difference (P(a-ET)CO2) were studied in 16 ASA-I patients anesthetized for laparoscopy under controlled ventilation. Using constant ventilation throughout the procedure, PaCO2 and PetCO2 increased significantly (P less than 0.01) to the maximum level (about 10 mmHg above the control level) within 22 min after CO2 insufflation, along with significant increase in mean arterial pressure and heart rate. There was a statistically significant correlation between PaCO2 and PetCO2 at the time of control (before surgery), at the time of maximum PetCO2 and 30 to 60 min after CO2 insufflation (P less than 0.01). Although mean P(a-ET)CO2 remained relatively constant during the procedure, a statistically significant correlation between PaCO2 and P(a-ET)CO2 was found at the time of maximum PetCO2 after CO2 insufflation (r = 0.71, P less than 0.01). These results suggest that when PvCO2 is increasing by CO2 insufflation, P(a-ET)CO2 depend on relative ventilation efficacy.